An irreverent trip through four billion years of evolution, this freewheeling excursion combines swaths of paleontology, geology and natural history, travel notes and amateur fieldwork from Kansas to British Columbia, amplified by wacky cartoons and colorful, often fantastical mixed-media drawings. Matsen and Troll, who collaborated on Shocking Fish Tales , emphasize that we are descended from fish that came ashore some 375 million years ago, giving rise to land-dwelling vertebrates. Evolution emerges here as a series of mass extinctions, improbable survivals, false starts and unsolved enigmas. Although their jocularity often impedes the narrative, Matsen and Troll bring a sense of awe and excitement to an informative, magical tour that is a lot more fun to read than standard texts and responsibly covers current scientific controversies. (Aug.)